My wife Liz has the most wonderful laugh. When something strikes her as really funny -- and you never can be quite sure why or when that will be -- she loses control completely. Her eyes close, she whoops, she screams, she roars. One of my favorite things is to render her helpless in that way.
She has recently taken laughter to another level, as a certified laughter yoga leader. Check out laughteryoga.org, it's good for you.